Page 234 - Carbonate Platforms Facies, Sequences, and Evolution

or
or
the
and
sets.
zoans
metre
These
facies,
sparse
above,
spicules
very
(Figs 15
bonate).
marly
to
following
(northern
of
and
tinguished:
&
argillaceous
When
ammonites).
and
dasyclad
consist
the
Free
coarse
order
subtidal skeletal
of
pelagic fauna
of
on the one hand,
Valanginian -early
small
first
independent
crinoids;
limestone.
limestone and marl,
algae)
Subalpine
metre-thjck
has
or submergence facies.
complete,
above
debris
of
sponge spicules.
grains;
(2)
the two extremes of the
wackestone
quartz
bedded
Urgonian platform margin
Two
the
the
they
and
chains).
Urgonian
arranged
with
facies of the Urgonian plat form
(corals,
Hauterivian
blue or ochre in colour due to
practically
foraminifera,
A
are
sea-level
alternations
bioclastic
large
of
and
poorly-sorted
microfacies
hemipelagic
fourth
ljmestone
glauconite,
(2)
can
arranged
variation
iron oxides.
'ball-shaped'
with high clay content,
quartz, glauconite, radiolaria and ammonites.
in well-sorted
limestone
palaeogeography,
transgression
coarse debris and low clay content (87 -100%
Vocontian Basin pelagic and hemipelagic facies
be
Glauconite is present,
in
they
facies:
group
Lowstand wedge bioclastic facies and outer-shel f
packstone­
dis­
car­
The pelagic facies are represented by regular deci­
bryo­
grainstone with little or no clay and dominant deep­
milli­
also be added, grouping together the facies linked to
may
curve:
and on the other, illgh-level and transgressive and/
deposited during the late Barremian transgression.
irregular alternations of marl and marly limestone,
and,
Lowstand wedge located in the Vocontian Basin and
but
low-level and emergence facies,
16) grouped together in parasequence
These
argillaceous
facies are arranged in shallowing-upward sequences
The hemipelagic facies are represented either by
(1)
the
wackestone-packstone with clay, silted quartz and
The third region is represented by inner Urgonian
silted
deposited after the maximum deepening of the late
disappeared (few
sequence
platform facies deposited on both the Jura domain
peloidal
(1) mudstone-wackestone with sponge
are
with
of
and in the northwest part of the Dauphinais Basin
foraminifera
metric beds, alternately fine and coarse (influence of
(3) grainstone with coarse
at
of
with
form
made
facies
1977).
stone,
1 km);
wedge
the
lowstand
(2)
the
and,
and
patch-reefs.
Hauterivian
bioclasts
hemipelagic
base
gullying
accumulation
(northeastern
parasequence,
to
very
(northern
of
The
The Jura and northern Subal pine chains
wedge,
Hauterivian facies
steep
mud.
above
and
French
more gentle slope.
from
suggests
Diois)
all,
rapid
transgressive sequence,
very
fairweather wave-base.
a
that
outer
nature
These
the earlier Jura platform.
by
without
Vercors),
of
features to be distinguished:
far
and
permit
'calcaires a
vertical
slope
change
any
shallow-subtidal
the
hemipelagic
and always containjng glauconite,
less
features
marls
at
three
from
to their palaeogeographical position
upon
poorly-sorted
Jura platform
vertical
up of very coarse debris locally
in
passage,
miches')
facies
the
facies and Urgonian limestone
transition
indicate
to
which
coarse
rapid and
alternate
a
Chartreuse
in
top.
The outer regions of the Urgonian platform,
the waves?); and (4) oolitic grainstone with cross­
On the slope of the outer shelf of the Jura plat­
gradual vertical and lateral passages (generally 4-
mor­
argillaceous limestone in wavy beds (nodular lime­
are presently known for comparisons to be made.
and coral reefs to hemipelagic facies (in places <
relation to
which probably exists at the Belle-Motte Mountain
deep-subtidal
Berriasian (unpublished) and that of the early Aptian
commonly
Nevertheless, the southern Vercors early Barremian
late
fundamental
distribution
sedimentological features indicate deposition above
bedding. This top level is locally overlain by small
Too few examples of bioclastic lowstand wedges
(as in the Little Bahamas Bank; Hine & Neumann,
The
each
coarse
bioclastic facies; and (3) presence of bioclastic facies
(1) very rapid lateral
seaward passage from oolitic shallow-subtidal facies
219
more
with
on
the other hand, are characterized by finer bioclastic
mixed with
sands
hemipelagic facies. This is usually associated with a
5 km) between shallow-subtidal bioclastic facies and
heavy
differ according
phology containing many contrasts: small reefs and
These facies (Figs 17 & 18), more-or-less argillaceous
narrow oolitic shoals on the edge of the lowstand
containing
storms (cyclones?) brought about several metres of